Photographic reversal copying process



March I 7, 1950 E. YACKEL PHOTOGRAPHIC REVERSAL COPYING PROCESS 2 Sheets-She et 2 Filed June 2, 1948 ease 405060 GEL/I TIN EDWARD C .YACKEL INI'LNI'OK "11.0w;

Patented Mar. 7, 1950 PHOTOGRAPHIC REFERSAL COPYING PROCE Edward C. Yackel, Rochester, N. Y., assignor to' Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application June 2, 1948, Serial No. 30,543

11 Claims. I

This invention relates to a photographiccopying process and more particularly to a reversal copying process utilizing relief images.

In the past a number of processes have been proposed for the reproduction of images by means of colloid reliefs. In the conventional method a dichromate sensitized colloid layer is exposed to a suitable subject and as a result the layer is hardened in the region of the exposure and the balance of the layer may be removed by treatment with hot water. The result is a negative hardened gelatin relief image in respect to the original subject. More recently a process for forming positive relief images directly from an original subject has been proposed wherein a dichromate sensitized mixture of gelatin and a synthetic resin, after exposure and treatment with aqueous solutions, yields a positive relief image. A process of this type is described in Staehle U. S. Patent application Ser. No. 558,346, filed October 12, 1944. One disadvantage of such processes lies in the inherently low speed of the dichrornate sensitized compositions, it generally being required to expose the sensitive materials to high intensity light sources such as carbon arcs.

I have found that the sensitivity of a composition designed for the production of positive relief images may be greatly increased by the substitution of silver halide for dichromate. However, in order to produce a direct-positive relief image it is necessary to employ a tanning development step in my process. The surprising result of using this tanning development step in connection with my compositions is that a positive relief image is obtained compared-to the usual negative relief image which is ordinarily obtained by using gelatin compositions containing silver halide as the sensitizing material.

One object of my invention is to provide the sensitive materials suitable for carrying out a reversal copying process by means of relief images. A further object of my invention is to provide various methods by which the sensitive materials may be used for producing direct positive relief images. Other objects of my invention will become apparent from consideration of the following description.

The objects of my invention are accomplished by exposing to a subject a light-sensitive layer containing a mixture of gelatin, polymerized acrylic ester resin and silver halide, then developing the exposed layer in the presence of a tanning developing agent followed by treatment with warm water in order to remove the colloid layer in the regionof the exposure, and subsequently, if desired, exposing and developing the silver halide in the positive relief image remaining on the support.

In the accompanying. drawings, Fig. 1 shows in enlarged cross-sectional view the appearance of the sensitive photographic element of my invention at various stages in the process of producing a direct positive relief image. Fig. 2 is a ternary diagram showing preferred compositions of the silver halide sensitized layer useful in carrying out my process.

My invention will be understood by a consideration of the following example in reference to the accompanying drawings.

Example To one kilogram of five per cent aqueous gelatin solution containing 30 grams of silver bromide. is added 240 cc. of a 25 per cent aqeuous colloidal dispersion of polyacrylic ester resin containing grams of solid resin. Of this amount of resin approximately per cent is polyethylacrylate resin and the balance polyacrylonitrile resin.

The composition is coated on a cellulose acetate film support subbed with a layer of cellulose nitrate and the resultant coating dried at a moderate rate in a chamber provided with a current of warm air. The appearance of the sensitive material is shown in the first stage of Fig. 1 of the accompanying drawings wherein support ll carries the subbing layer ll over which. is the emulsion layer I2 composed Of the mixture of gelatin, resin'and silver halide. The film is ex-.

posed by projection to a suitable subject under conditions customarily used for exposing moderately high speed silver bromide photographic emulsions. After exposure, the element is bathed for 90 seconds in a one per cent aqueous hydroquinone solution and then treated in a five per cent aqueous sodium carbonate solution for about 30 seconds. The appearance of the film at this point is shown in the second stage of Fig. 1 of the accompanying drawings wherein the support In provided with the subbing layer I I now carries emulsion layer I! having tanned image areas I 3 containing silver. In order to produce the desired relief image the developed element is treated with water at approximately 60 C. as a result of which tanned image areas It flake-oil the support leaving a positive relief image as shown inthe third stage of Fig. 1 of the accompanying drawings wherein the subbed support now carries the relief image H consisting of gelatin, resin and silver halide and areas it of the support are substantially free 01 emulsion. If a coloring ma- I shown as carrying the relief image I6 consisting of gelatin, resin and silver.

My invention is subject to a number of variations, both in the composition of the sensitive emulsion layer andthe manner of processing the same. For example, the emulsion layer may be composed of a mixture of gelatin, acrylic ester resin and silver halide in various proportions. I find it desirable to provide the emulsion with sufficient gelatin to obtain the desired degree of tanning, and the optimum amount of silver halide is used to obtain sensitivity and to provide sufficient oxidized developer for tanning of the colloid layer after exposure. To this end the best results are obtained by use of the following representative proportions of materials:

I'crcent Percent Percent Gelatin Resin Silver Halide Another way of expressing the preferred proportions of the materials is to say that when th ratio of resin to gelatin on a dry basis is about 60 per cent, the ratio of gelatin to silver halide is of the order of three parts of gelatin to two parts of silver halide. If the ratio of gelatin to silver halide is shifted in favor of the gelatin, that is, three Parts gelatin to one part silver halide, the .preferred ratio of resin to gelatin is about 70 per cent. If the ratio of the gelatin to silver halide is shifted in favor of the silver halide to one part of gelatin to one part of silver halide the preferred resin to gelatin ratio is 55 per cent.

The above preferred emulsion compositions are representative of a group of emulsions having the compositions lying on curve AB of the ternary diagram of Fig. 2 of the drawings which group constitute a preferred embodiment of my invention. In the diagram, the terminal points of curve AB represent compositions shown in the table above. The proportions of the emulsion constituents may be varied somewhat depending upon the particular resin, silver halide, gelatin or tanning developing agent used. For example, the above ratios are very effective when the resin and silver halide are those described in the above example but with different gelatin samples, acrylic ester resins, silver halides or developing agents it may be desirable to alter the proportions somewhat to produce optimum results. It is apparent that at all times suificient silver halide should be present in the original emulsion to provide sufficient silver to effect tanning of the colloid layer. Acrylic resins suitable for use in the emulsion are for example, polymerized lower alkyl esters as methyl, ethyl, propyl or butyl esters of acrylic acid and alkyl substituted 4 acrylic acids such as ethyl acrylateymethyl acrylate, methyl methacrylate, etc. Also the resin component of the emulsion may consist of a mixture of resins or copolymerized resins. Such resins are, of course, used only in the form of aqueous colloidal dispersions so they may be mixed with the gelatin emulsion.

The'supporton which the sensitive laver s coated is somewhat critical in that it should consist of a hydrophobic colloid material from which the exposed and tanned negative image can be removed with hot water but to which the untanned emulsion will adhere. The best results are obtained with a support having a surface of a cellulose ester such as cellulose nitrate or a synthetic resin such as a polyvinyl acetal resin particularly a polyvinyl butyral resin. Of course such surfaces may be a part of a support such as wood, cloth, paper and the like.

The developing agent used in conjunction with the tanning developing step of my process may be incorporated either into the original emulsion or in a separate solution used for treating the emulsion subsequent to exposure. Hydroquinone and pyrocatechol are suitable for use as described in the above example. When the developing agent is incorporated into the emulsion layer, tanning development is effected after exposure by treatment of the layer with an alkalin solution such as sodium carbonate or sodium hydroxide.

In the process of forming a relief image in the manner of the above example, I can incorporate a coloring material such as a white or black pigment, for example, titanium dioxide on carbon, or a dye, into the original emulsion with the result that it is not necessary to carry the process beyond the third stage shown in Fig. 1 of the drawings; that is, the final exposure and development steps are not required. The use of such materials in the emulsion of course reduces the speed of the sensitive element. Variations in speed of the sensitive material can be controlled in a well known manner by selection of the particular silver halide or type of sensitizer therefor. The delineation of the relief image shown in the third stage of the Fig. 1 of accompanying drawings may also be increased by known dye imbibition methods or methods of color development. In the latter case I can incorporate the coupler compound either into the emulsion layer or the color developing solution and color development of an image in the relief is carried out in a manner well known to the art.

It is to be understood that the disclosure herein is by way of example and that I consider as included in myinvention all modifications and equivalents falling within the scope of the appended claims.

What I claim is:

1. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer selected from those having compositions lying on curve AB of Fig. 2 of the attached drawings and being coated on a hydrophobic colloid surface, developing said exposed emulsion layer in the presence of a tanning developing agent and treating said layer with warm water to effect removal of only the tanned image area from the support.

2. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer selected from those having compositions lying on curve AB of Fig. 2 of the attached drawlugs and being coated on a hydrophobiccollold surface, developing said exposed emulsiofflayer in the presence of a tanning developing agent, thereby producing a tanned silver-containing colloid image in the region of said exposure, treating salddayer with warm water to effect removal of only the tanned image area from the support, and increasing the delineation of the colloid relief image remaining on said support.

3. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer selected from those having compositions lying on curve AB of Fig. 2 of the drawings and being coated on a hydrophobic colloid surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region of said exposure, thereafter treating said layer with warm water to effect removal of only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support.

4. A photographic copying process which comprises exposlng to a sub ,ect a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially equal amounts of gelatin and silver halide and about '7 per cent more acrylic ester resin than gelatin, said emulsion being coated on a hydrophobic colloid surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region of said exposure, thereafter treating said layer with warm water to effect removal of only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support.

5. A'pnotographic copying process which coinprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially three parts gelatin per two parts silver halide and about 16 per cent more acrylic ester resin than gelatin, said emulsion being coated on a hydrophobic colloid surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region of said exposure, thereafter treating, said layer with warm water to effect removal of only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support. I

6. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially three" times as much gelatin as silver halide and about 37 per cent more acrylic ester resin than gelatin, said emulsion being coated on a hydrophobic colloid surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region of said exposure, thereafter treating said layer with warm water to effect removal of only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support.

7. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially equal amounts of gelatin and silverhalide and about 7 per cent more acrylic ester resin than gelatin, said emulface, developing said exposed emulsion layer with sion being coated on a cellulose nitrate surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region of said exposure, thereafter treating said layer with warm water to effect removal of. only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support.

8. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially three parts gelatin per two parts silver halide and about 16 per cent more acrylic ester resin than gelatin, said emulsion being coated on a cellulose nitrate surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region. of said exposure, thereafter treating said layer with warm water to effect removal of only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support.

9. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially three times as much gelatin as silver halide and about 37 per cent more acrylic ester resin than gelatin, said emulsion being coated on a cellulose nitrate surface, developing said exposed emulsion layer with a tanning developing solution to produce a tanned silver-containing colloid image in the region of said exposure, thereafter treating said layer with warm water to effect removal of only the tanned image from the support, and developing a silver image in the colloid relief image remaining on said support.

10. A photographic copying process which comprises exposing to a subject a light-sensitive gelatino-polyacrylic ester-silver halide emulsion layer containing substantially equal amounts of gelatin and silver halide and about seven per cent more ethyl acrylate resin than gelatin, said emulsion being coated on a cellulose nitrate sura tanning developing solution to produce a tanned prises exposing to a subject a light-sensitive gelatino-polyacrylic ester resin-silver halide emulsion layer coated on a support having a hydrophobic colloid surface, said emulsion layer containing from approximately 27 to 36% gelatin, from approximately 38 to 64% polyacrylic ester resin, and from approximately 9 to 31% silver halide, the ratio of gelatin to silver halide being from approximately 1:1 to 3:1 and the ratio of gelatin to resin being from approximately 1:1.2 to 112.4, developing said exposed emulsion layer in the presence of a tanning developing agent to produce a tanned image in the exposed area, and treating said layer with warm water to remove only the tanned image area from the support.

EDWARD C. YACKEL.

REFERENCES CITED 2,006,002 2,184,310 The following references are of record in th file of this patent: v

5 Number UNITED STATES PATENTS 384,312 Number Name Date 549 1,981,102 Hagedorn Nov. 20, 1934 573,771

8 Schneider June 25, 1935 Melgs Dec. 26, 1939 FOREIGN PATENTS Country Date Great Britain Nov. 30, 1932 Germany Dec. 29, 1934 Great Britain Dec. 5, 1945 

11. A PHOTOGRAPHIC COPYING PROCESS WHICH COMPRISES EXPOSING TO A SUBJECT A LIGHT-SENSITIVE GELATINO-POLYACRYLIC ESTER RESIN-SILVER HALIDE EMULSION LAYER COATED ON A SUPPORT HAVING A HYDROPHOBIC COLLOID SURFACE, SAID EMULSION LAYER CONTAINING FROM APPROXIMATELY 27 TO 36% GELATIN, FROM APPROXIMATELY 38 TO 64% POLYACRYLIC ESTER RESIN, AND FROM APPROXIMATELY 9 TO 31% SILVER HALIDE, THE RATIO OF GELATIN TO SILVER HALIDE BEING FROM APPROXIMATELY 1:1 TO 3:1 AND THE RATIO OF 